Massive Klein tunneling in topological photonic crystals

Klein's paradox refers to the transmission of a relativistic particle through a high potential barrier. Although it has a simple resolution in terms of particle -to -antiparticle tunneling (Klein tunneling), debates on its physical meaning seem lasting partially due to the lack of direct experimental verification. In this article, we point out that honeycomb -type photonic crystals (PhCs) provide an ideal platform to investigate the nature of Klein tunneling, where the effective Dirac mass can be tuned in a relatively easy way from a positive value (trivial PhC) to a negative value (topological PhC) via a zero -mass case (PhC graphene). Specifically, we show that analysis of the transmission between domains with opposite Dirac masses-a case hardly be treated within the scheme available so far-sheds new light on the understanding of the Klein tunneling. (c) 2024 Optica Publishing Group under the terms of the Optica Open Access Publishing Agreement